Interface Chemistry Evolution and Leakage Current Conduction Mechanism Determination in Rare-Earth-Doped Hf-Based Gate Dielectrics

In this work, the effects of Rare-Earth (RE) doping (Y, Gd, Dy, Yb) in HfO
₂
on the interface chemistry and leakage current conduction mechanism of Ge-MOS devices have been explored. The electrical experimental results have indicated that
${\text{HfREO}}_{\!{x}}$
(RE = Gd and Dy) show excellent performance, including the reduced flat-band voltage, almost disappeared hysteresis, and the decreased leakage current, which can be attributed to the tradeoff of performance between lanthanide-based oxides and HfO
₂
. X-ray photoelectron spectroscopy (XPS) measurements also display that
${\text{HfGdO}}_{\!{x}}$
and
${\text{HfDyO}}_{\!{x}}$
gate dielectrics can effectively inhibit the formation of unstable Ge suboxides and low-
${k}$
germanate interface layer, leading to the reduced defect state at/near the interface and the improved electrical performance. In addition, the doping element-dependent leakage current conduction mechanism of Ge-based MOS devices under low temperature has been investigated systematically. As a result, it can be inferred that RE doping has a significant impact on Hf-based MOS capacitors, and Hf-based gate dielectrics doped with heavy RE elements show excellent application prospects in future microelectronic devices.